What is a sexually transmitted infection?

A sexually transmitted infection (STI) is an infection you can get by having sex. Some STIs (such as gonorrhea and Chlamydia) infect your sexual and reproductive organs. Others (HIV, hepatitis B, syphilis) cause general body infections. STIs used to be called VDs, or venereal diseases.

An STI is spread during sexual activity. It is spread during vaginal, anal and oral sex. Some STIs (HIV and hepatitis B) are also spread by contact with infected blood. STIs are not normally spread by digital sex (fingering); however, unclean hands or uncut nails can cause genital problems.

Most STI germs need to live in warm, moist areas. That's why they infect the mouth, rectum and sex organs (vagina, vulva, penis and testes).

Most STIs can be cured if you seek treatment. Sometimes you can have an STI with no signs or symptoms. Other times, the symptoms go away on their own. Either way, you still have the STI until you get treated. Some STIs cannot be cured.

• How Can I Tell if I Have an STI?


• What to Do If You Think You May Have an STI


• How to Protect Yourself from an STI


• Safe Sex and Levels of Risk


• Oral Sex and STI Risk

Last reviewed January 2009
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